Cooling the inductors of turbo-generators



June 2, 1936 F. PUNGA ET AL COOLING THE INDUCTORS OF TURBO GENERATORS 2 sheets-sheet 2 Filed Sept. lO, 1934 fyi@ CIL.

Patented June 2, 1936 UNiTED STATES PATENT OFFICE COOLING THE INDUCTORS OF TURBO-GENERATORS Application September 10,

1934, Serial No. 743,466

In Germany September 30, 1933 13 Claims.

This invention relates to the cooling of the inductors of large turbo-generators.

The longer the inductor of a turbo-generator, the more diiiicult it is to force the requisite cooling air into the middle of the coil. The heat given out per unit area of the coil and per degree centigrade of temperature rise is then less, and since the heating of the air becomes greater and consequently the temperature rise available grows less, there ensues a reduction in the required current density.

The object of the present invention is to provide an arrangement, whereby a substantially improved cooling of the induction coils and of the whole oi the inductor is obtained.

According to this invention an arrangement for cooling the inductor of a turbo-generator is provided wherein in a trapeze-shaped slot in the inductor, two coils are disposed which fit against the side walls and leave a trapeze-shaped air space in the middle, which receives cool air from the space between the stator and the inductor.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which Fig. l represents a section through a slot in a wound inductor, and

Figs. 2 to i3 represent various arrangement.

Reierring to the drawings, Fig. l shows a section through a slot in a wound inductor in which instead of one coil, two coils I and 2 are provided in each slot, which coils fit tightly against the walls ci the ,'trapezeshaped slots, and leave a trapeze-sh'aped air space 3 in the middle. The aerating of this middle space iscarried outthrough an air passage made possible by a special construction of the iixing-wedges so that a suicient amount of fresh air is led from the stator ribs to the air passage, which may be easily effected in known manner. The fixing-wedge 4, which is in general made of non-magnetic steel, has a passage cut therein which fulfills the function of drawing air into the middle of the slot due to the direction of revolution given by the shaft. In another xing-wedge 41 another passage is cut in the shape as shown at lil (Fig. 2). The opening or" this passage is directed in the opposite direction to the direction of revolution and air is sucked out of the inside of the slot.

In the preferred form of construction of the coils and the fixing-wedges the windings oi the coils' l and 2 are not wound in one piece, but use is made of hard-pressed and hard-baked hemishaped coils (for example according to German details of the specication No. 558,081) whose face connections are continuously welded together. Figs. 8a and 8b show a simple manner of connecting these hemi-shaped coils together.

A single conductor is made from two components which viewed from above has the shape as shown in Fiig. 8b and from the side the shape as shown in Fig. 8a. Both components have about the same section, are either welded or riveted together and are placed end to end, so that the hemi-section projects from the end of the coil and can be easily welded outside the coil. The reduction in size of the section at the end can also be brought about by using a single conductor and ling the ends. In this way the separate heini-coils, previously pressed and baked, can be iitted into the slots through the slot opening. In this position the conductors of the hemi-shaped coil are for the rst time welded to the conductors of the hemi-shaped coil corresponding thereto.

In order to affix the coils iirmly to the side walls, proportionately small distance pieces 8 (Fig. 3) made of hard paper or micanite or insulated aluminium pieces are provided, which have the same section as the air space 3 shown in Fig. l and which, after the two coils have been placed in position, are pressed or driven into the body of the slot. The space between two distance-pieces forms an air chamber, which requires for the necessary aeration openings of the shape 5, Fig. 1, or openings of the shape I0, Fig. 2. Distance pieces can be used, which have axial hollow air passages, such as a distance-piece as shown in 4, which has axial slots therein.

The wedge is best fixed, not directly onto the end of the coil, but onto a plate 6 (Fig. 1) which has numerous air holes through the middle thereof. Some of these airholes act at the same time to prevent movement of the distance pieces, for example if the distance pieces have dowel pins on the top as at 9 (Fig. 3) which engage in the air holes of the separating plate 6. In order to facilitate the pressing of the wedge into position, the upper side of the plate and the under side of the wedge are provided with small rivets. On recognized mechanical grounds the end of the slot in the slot body is not made rectangular but with a gradual rounding oir so that a supporting piece i i can be laid therein. The remaining free space is also utilized for ventilation and pieces cut away from this supporting piece Il allow direct access of air to the space 3.

The iron body of the inductor is also advantageously cooled in like manner. Fig. 5 shows an unwound slot which serves chiefly for the aeration of the iron body of the inductor. The wedge again has a passage out therein which at the top is inclined either in the opposite or the same direction as the direction of revolution and either draws in or expels air. The wedges are made of either magnetic or non-magnetic material. If a powerful damping winding is desired, it is preferable to construct the wedge of copper and to give it a substantially large section, for in combination wtih the aforementioned cooling arrangements, cooling of a copper wedge can be made especially efficient. The inner surface of this cooling slot can be made more effective by means of flutings.

The non-magnetic wedges of the non-wound and those of the wound slots can also project out of the magnetic surface, so that the passages in the wedge slots are made more effective. Such a wedge is shown in Fig. 6. The parts adjoining the face joints are more effectively disposed in the axial direction of the effective length of the inductor than those arranged in the middle, for 'fresh air can be brought in from both sides of the centre of the slot 3. It is therefore advantageous to employ at both ends, the distance pieces slotted as in Fig. 4 and only to fix the passages 5 in the wedge at a certain distance from the end surfaces of the coils I and 2.

The passages can also be arranged to lie partly in the wedge and partly in the tooth of the inductor, as shown in Fig. 7. The idea can also be utilized in connection with inductors built according to the A. E. G. (Allgemein Elektrisch Gesellschaft) construction, in which only a single coil, which is pressed and baked, lies in a slot, and in which an air space is left between the coil and the walls of the slot. Air from the air crevices can therefore be forced in and sucked out of the air spaces through suitable passages cut in the inductor tooth and the wedge, so that the air is also forced in this case first to flow along the axial direction of the coil, before leaving the air space.

If the wedge is constructed as shown in Fig. 6, it is unnecessary for the total width of the wedge to project over the upper surface of the inductor, for it is suicient to have a few centmetros extending above the passage opening.

The projection from the upper surface of the inductor can be limited to those passages that force the air into the inductor slot.

In the case of the unwound slot according to Fig. 5 it is advantageous to separate with distance pieces the inner part of the inductor, which has to be cooled with air from the air crevices, from the two outer parts which are to be cooled with air from the two ends of the inductor.

The utility of the inductor can be increased if the cross section of the coil is not rectangular but trapeZe-shaped. The part of the cross-section lying at the opening of the slot will be increased, whilst the cross-section in the bottom of the slot remains the same. The air space left according to Fig. l is therefore either rectangular or it remains trapeze-shaped, but with a substantially smaller upper edge. This latter condition is preferable, as distance pieces are to be fitted in fixed positions, which are preferable with a trapezeshaped section.

According to the invention the cross-section of the coil faces at the end connections is rectangular, and the section of each single conductor can be as great as the largest section of a conductor in the slot, or even greater, especially if aluminium is used as winding material. With the cooling arrangement of the present invention it is possible to cool the inductor slot very efficiently and much more efficiently than the face connections. Since, however, it is most desirable to maintain an even temperature rise in all parts of the inductor winding, the cross-section of the single conductor at the face connection is increased. If copper winding is used, however, this enlargement requires consideration on other grounds, for in the case of large turbo-generators the compensation of the centrifugal force in the face connections presents an extremely difficult problem, for which a solution has been sought by such considerations as the diminshing in size of the cross-section of the conductors in the face connections in opposition to the cross-section of the slot parts. The use of aluminium winding is helpful here as the action of the centrifugal forces are substantially smaller than when copper winding is used. The manufacture of a coil with varied cross-section at the face connections and the part in the slot can be accomplished if the coil is first made as described above with the same cross section throughout and then subsequently shaped off to the cross-section of the part in the slot. Provision must be made in this case for a gradual change from the cross-section in the slot part to the cross-section at the face connections. If., however, heini-shaped coils are used, viz. as described in German specification No. 558,081, then the cross-section of the coil can naturally be correctly shaped from the beginning, and in the latter case a slight disadvantage can be removed, which according to the method of winding chosen must be taken into account in the cost.

By altering the thickness of the conductor the current density in the part laid in the slot can be taken as equal to or nearly as great as the part of the cross-section lying at the slot opening.

If use is not made of the hemi-coils or of the previous pressing and baking, so that the coils can be placed as one piece in the slot, then the arrangement as described herein can be varied in several ways, for then it is possible to aerate the coil from the inside, without mechanically splitting it into two parts. For example rectangular or oval slits can be stamped out of the conductors of the coils themselves (Fig. 9) which then take the place of the trapeze-shaped empty spaces of Fig. 1. It can also be carried out by making two successive slits separated from each other in the upper half of the coil but coming together in the lower half of the coil, so that the air is forced to flow downwards in one slit and upwards in the other slit. To accomplish this it is only necessary that the one slit is connected with an opening in the wedge in the direction of rotation and the other slit connected with an opening in the opposite direction. The coil can also have pieces cut away from the sides somewhat as shown in Figs. 10a and 10b. With this latter arrangement it is possible to cause the air to flow on one side downwards and on the other side upwards, as shown in Fig. 11. The above idea can be applied in many ways to the construction with inset teeth well known to those skilled in the art under the name A. E. G. construction. For example the teeth may have parts cut away as in Fig. 12, whereby the air is forced to flow on both sides of one tooth downwards and on both sides of another tooth upwards. In this case the swallow-tailed slot, in which the inductor tooth is fixed, must be provided with a large axial air cross-section, and

amargos theseV air channels .mustbe connected together at suitable axial intervals.

Asshown in Fig. 13 air can also be made to flow downwards on one side of the tooth and with thelaid of passages cut away to Vflow upwards on rotor being provided with slots, coils carried in the slots of said rotor, said slots being larger than the coils thereby providing cooling air channels, means for drawing cooling air from the space between stator and rotor into the rotor slots at one point and for sending the air back to the said space at an axially spaced point after cooling the rotor coils whereby the cooling air moves inwardly and axially before being expelled out- Wardly.

2. In a dynamo-electric machine having an external stator and a rotor within the stator, said rotor having slots opening at the periphery thereof, two coils in each slot of said rotor leaving an air space between them, means for drawing cooling air from the space between stator and rotor into the rotor slots at one point and for sending the air back to the said space at a point axially spaced from the rst point after cooling the rotor coils whereby the cooling air moves inwardly and axially in the rotor before being expelled outwardly.

3. In a dynamo-electric machine having an external stator and a rotor within the stator, said rotor having slots, two coils in each rotor slot leaving air spaces between them, the rotor also having axially spaced cooling air inlet and outlet passages opening at the periphery thereof and communicating with said air spaces, said inlet passages being curved forwardly in the direction of the rotation of the rotor, and said outlet passages being curved rearwardly in the opposite direction respectively for drawing cooling air from the space between the stator and rotor into the air spaces of the rotor slots and for sending the air back to the space between said stator and rotor after cooling the said coils whereby the air moves inwardly and axially in the rotor slots before being expelled outwardly.

4. In a dynamo-electric machine having an external stator and a rotor within the stator, said rotor having radially extending slots opening at `the periphery, two coils in each rotor slot leaving air spaces between them, coil xing wedges in said rotor slots, said` wedges having passages curved in the direction of the rotation of the rotor and opening to the space between the stator and rotor and with passages curving m the opposite direction and opening to the the space between said stator and rotor, respectively, for drawing cooling air from the space between stator and rotor into the air spaces of the rotor slots and for sending the air back to the space between the stator and rotor after cooling the coils.

5. In a dynamo-electric machine having an external stator and a rotor, said rotor being provided with slots, hard pressed and backed hemishaped coils disposed in said rotor slots and leaving air spaces therein, means providing an inlet and an outlet for drawing cooling air from the space between stator and rotor into the rotor slots and for sending the air back to the said space after cooling the rotor coils, the inlet and outlet being axially spaced apart, whereby the air moves inwardly, and axiallyfbefore.:being expelled outwardly;

6,. In a.V dynamo-electric machine having a stator and rotor, said rotor being provided with slots, Atwo hard pressed andbackedhemi-shaped coils ineach rotor slotv leaving; air -spaces between them, means providing an inlet andf an outlet for drawing cooling air from the space between the stator and rotor into; the rotor slots and for sending the air back/to theisaidf Space after cooling therotor coils;y theainlikand: outlet being axially spaced apart, whereby the air moves inwardly, and axially before being expelled outwardly.

7. In a dynamo-electric machine having a stator and a rotor, said rotor being provided with slots, two coils in each slot leaving an air space between them, fixing wedges for the coils in the rotor slots, the rotor having teeth overlapping the wedges, said teeth and wedges being provided with passages extending in the direction of the rotation of the rotor and With passages extending in opposite direction for drawing cooling air from the space between stator and rotor into the rotor slots and for sending the air back to the said space after cooling the rotor coils, substantially as and for the purpose described.

8. In a dynamo-electric machine having a stator and a rotor, said rotor being provided with slots, two coils in each rotor slot leaving an air space between them, xing wedges for the coils 9 in the rotor slots, said Wedges having passages extending in the direction of the rotation of the rotor and passages extending in the opposite direction for drawing cooling air from the space between stator and rotor into the rotor slots and U for sending the air back to the said space after cooling the rotor coils, and a plate having periorations arranged between each iixing Wedge and the coils.

9. A dynamo-electric machine having a stator and a rotor, said rotor being provided with slots, two coils in each rotor slot leaving an air space between them, non-magnetic xing wedges for the coils having passages therein extending in the direction of the rotation of the rotor and having passages extending in opposite direction for drawing cooling air from the space between the stator and rotor into the rotor slots and for sending the air back to the said space after cooling the rotor coils, the xing wedges projecting out- E' wardly beyond the periphery of the rotor.

10. A dynamo-electric machine having a stator and a rotor, said rotor being provided with slots, coils disposed in said rotor slots and leaving air spaces therein, means for drawing cooling air from the space between stator and rotor at one point into the rotor slots and for sending the air back toy the said space at a point axially spaced from said first point after cooling the rotor coils, and distance pieces of insulated material between the coils.

11. A dynamo-electric machine having a stator and a rotor, said rotor being provided with slots, two coils in each rotor slot leaving an air space between them, fixing wedges for the coils in said rotor slots and having passagesvformed therein extending in the direction of the rotation of the rotor and having passages extending in the opposite direction for drawing cooling air from the space between the stator and the rotor into the rotor slots and for sending the air back to the said space after cooling the rotor coils, and distance pieces of insulated material provided with channels between the coils.

12. A dynamo-electric machine having a stator and a rotor, said rotor being provided with slots, coils disposed in said rotor slots and leaving air spaces therein, means for drawing cooling air from the space between stator and rotor into one rotor siot at one point and for sending the air back to the said space through a neighboring rotor slot at a point axially spaced from the rst point after cooling the rotor coils.

13. A dynamo-electric machine having a stator and a rotor, said rotor being provided with slots,

two coils in each rotor slot leaving an air space between them, xing wedges for the coils disposed in said rotor slots and having passages extending in the direction of the rotation of the rotor and with passages extending in the opposite direction for drawing cooling air from the space between stator and rotor into one rotor slot and for sending the air back to the said space through a neighboring slot after cooling the rotor coils.

FRANKLIN PUNGA. HERMANN ROOS.

CERTIFICATE OF CORRECTION.

Patent No. 2,043,120, June 2, 195e,

FRANKLIN PUNGA, ET AL.

It is hereby ceroified that error appears in the above numbered paient requiring correction as follows; In Jfine heading, to the printed specifica Jsion, line 7, for Jhe foreign filing date "September .'50, 1933" read Octo- Der 5, 1935; and that the said. Letters Patent should be read with J:.his oorrecion therein that the same may conform 13o the record of the oase in the Patent Office.

Signed and sealed this 29th day of September, A. D. 1956.

Henry Ven Arsdale (Seal) Acting Commissioner of Patents CERTIFICATE: 0F ooRREmoN.

Patent No. 2,043,120, June 2, 1956g FRANKLIN PUNGA, ET AL.

It is hereby certified that eror appears in the above numbered patent requiring correction as follows; In the heading to the printed specifica.- tion, line 7, for the foreign filing date "Selfnaemoeir` ZO, 1933" read Octo- Der` 5, 1955; and that the said. Lettere Patent should be read with this oor'- reotion therein that the seme may conform to the record of the oase in the Patent Office.

Signed and Sealed this 29th dey of September, A. D. 1936.

.Henry Ven Aredele (Seal) ,e Acting Commissioner of Patents 

